Process for the acetoxylation of olefins in the gas phase

a technology of olefins and gas phases, which is applied in the preparation of carboxylic acid esters, chemistry apparatus and processes, and organic chemistry, etc., can solve the problems of increasing the total oxidation of the reaction mixture, limiting the concentration of starting materials, and reducing the yield of olefins, so as to improve the selectivity and the effect of low by-product formation and space-time yield

Inactive Publication Date: 2014-12-09
WACKER CHEM GMBH
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0020]It has now been surprisingly found that the use of a catalyst system comprising at least two catalyst zones which have differing reactivity and are arranged in layers in the flow direction enable achievement of a higher space-time yield, better selectivities with low by-product formation, combined with a virtually isothermal temperature profile in the catalyst bed.

Problems solved by technology

These temperature peaks (known as “hot spots”) bring about a series of undesirable effects during the course of the reaction.
Firstly, they limit a further increase in the starting material concentration (loading), which is equivalent to limitation of the space-time yield, and secondly an increase in total oxidation in the reaction mixture can occur (reduction in selectivity to the target product).
The latter is, in particular, reflected in a higher specific raw material usage and has a significantly negative effect on the economics of the process.
Furthermore, hot spots bring about premature aging of the catalyst.
Particularly in the case of fresh catalyst beds and also in the case of reactions with a high oxygen loading, irreversible damage to the catalyst can occur in this sensitive range when heat removal is insufficient.
The increasing product concentration can then again lead to inhibition of product formation and thus to a decrease in selectivity and conversion.
However, a disadvantage of this arrangement is the large outlay in terms of equipment.

Method used

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  • Process for the acetoxylation of olefins in the gas phase
  • Process for the acetoxylation of olefins in the gas phase

Examples

Experimental program
Comparison scheme
Effect test

example 1

Pd / Au Type Catalyst with Differing Promoter Contents

[0065]For this purpose, a catalyst was produced as described in WO 2008 / 071610 with the exception that the catalyst of the 1st zone contains 6.5% by weight of potassium and the catalyst in the 2nd zone contains 3.0% by weight of potassium.

[0066]

Designation1st Zone2nd Zone3rd Zonerelative5050—length [%]SiO2 support200200—BET (m2 / g)Pd (% by2.02.0—weight)Au (% by2.02.0—weight)K (% by6.53.0—weight)

[0067]This catalyst system according to the invention makes it possible to achieve maximum space-time yields of 980 g (VAM) / l of cat.*h at maximum ethene selectivities of 93.2% in the test in the reactor under the conditions described.

example 2

Pd / Au Type Catalyst Having Differing Support BET Surface Areas and Promoter Contents

[0068]Two catalysts were synthesized as described in WO 2008 / 071610; these differed in that the catalyst in the 1st zone was produced on SiO2 supports having a BET surface area of 150 m2 / g and a potassium content of 6.5% by weight and the catalyst in the 2nd zone was produced on SiO2 supports having a BET surface area of 220 m2 / g and a potassium content of 3.0% by weight.

[0069]

Designation1st Zone2nd Zone3rd Zonerelative5050—length [%]SiO2 support150220—BET (m2 / g)Pd (% by2.02.0—weight)Au (% by2.02.0—weight)K (% by6.53.0—weight)

[0070]This catalyst system according to the invention makes it possible to achieve maximum space-time yields of 1050 g (VAM) / l of cat.*h at maximum ethene selectivities of 93.5% in the test in the reactor under the conditions described. FIG. 1 shows the temperature profile of this two-zone catalyst system with a largely isothermal temperature profile with optimized catalyst util...

example 3

Pd / Au Type Catalyst with Differing EM Contents

[0071]Two catalysts were synthesized as described in WO 2008 / 071610; these differed in that the catalyst in the 1st zone was produced on SiO2 supports having a BET surface area of 180 m2 / g and a Pd and Au content of 2.0% by weight in each case and the catalyst in the 2nd zone was produced on SiO2 supports having a BET surface area of 220 m2 / g and a Pd and Au content of 2.3% by weight in each case.

[0072]

Designation1st Zone2nd Zone3rd Zonerelative6040—length [%]SiO2 support180220—BET (m2 / g)Pd (% by2.02.3—weight)Au (% by2.02.3—weight)K (% by6.53.0—weight)

[0073]This catalyst system according to the invention makes it possible to achieve maximum space-time yields of 1200 g (VAM) / l of cat.*h at ethene selectivies of 94.0% in the test in the reactor under the conditions described.

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Abstract

Yield and selectivity of olefin acetoxylation are improved through the use of successive catalyst zones of different reactivities, the successive zones contained in one or more reaction tubes arranged is parallel.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application is the U.S. National Phase of PCT Appln. No. PCT / EP2012 / 066390 filed Aug. 23, 2012, which claims priority to German application DE 10 2011 081 786.7 filed Aug. 30, 2011, the disclosures of which are incorporated in their entirety by reference herein.BACKGROUND OF THE INVENTION[0002]1. Field of the Invention[0003]The present invention relates to a process for the acetoxylation of olefins, in which a gaseous reaction stream containing an olefin, acetic acid and molecular oxygen is passed over at least two catalyst zones of differing reactivity arranged in series. Furthermore, the invention relates to a catalyst system for the gas-phase oxidation of olefins to form acetoxylated products, in particular for the preparation of vinyl acetate, which comprises at least two catalyst zones which are arranged in layers and have a reactivity matched to the course of the reaction.[0004]2. Description of the Related Art[0005]Processes f...

Claims

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Application Information

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Patent Type & Authority Patents(United States)
IPC IPC(8): C07C67/055C07C67/05
CPCC07C67/055C07C67/05C07C69/15
Inventor ROSCHER, ANJAEBERLE, HANS-JUERGENHEIDENREICH, ROLANDJUNG, HERBERT
Owner WACKER CHEM GMBH
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